Microtubules and their relationship to cell form in unicellular organisms are of major interest in this proposal. In the unicellular Ochromonas in vivo microtubule assembly and disassembly can be experimentally controlled using pressure, colchicine, or vinblastine. Ochromonas so treated are reversibly transformed to motile spheres. Efforts are being made to examine the nature of the microtubule nucleating sites which apparently direct the placement and timing of appearance of microtubules which result in the construction of the asymmetric Ochromonas. Isopropyl N-phenyl carbamate (IPC) has no effect on whole microtubules but either inhibits assembly or alters the nucleating site for the assembly of microtubules which have been disassembled with pressure. Experiments have been designed to test the hypothesis that IPC specifically affects the microtubule initiating site in these and other cells. A series of ancillary projects have been initiated to examine changes in the surface organization of experimentally treated cells and cells undergoing normal division. As cell form can be readily altered with microtubule depolymerizing ageets, it should be possible to follow the redistribution of the original surface in cells recovering from treatment. Flagellar surface growth, euglenoid pellicle origin and synthesis, and Ochromonas surface origin and behavior are being examined with antibodies labeled with peroxidase, fluorescein or ferritin specific for known surface components.